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Mathematics 21 Online
OpenStudy (studygurl14):

What do I do now? calculus problem @mathmale

OpenStudy (studygurl14):

OpenStudy (studygurl14):

@mathmale @hero @Zarkon

OpenStudy (zarkon):

\[e^{-x}\] is a decreasing function...just look at the endpoints

OpenStudy (studygurl14):

I have to do it without graphing.

OpenStudy (studygurl14):

@tkhunny @Hero

OpenStudy (zarkon):

you don't need to graph it

OpenStudy (zarkon):

\[f(x)=e^{-x}\] \[f'(x)=-e^{-x}<0\] and therefore it is decreasing

OpenStudy (zarkon):

since it is decreasing the max will be at \(x=-1\) and the min will be at \(x=1\)

OpenStudy (studygurl14):

Okay, thank you

OpenStudy (studygurl14):

What about the critical point part of the question?

OpenStudy (studygurl14):

@xapproachesinfinity

OpenStudy (xapproachesinfinity):

e^-x is strictly decreasing so there is no critical points

OpenStudy (xapproachesinfinity):

remember crtical point occur when the g' changes sign but here -e^-x <0 all the time no sign change

OpenStudy (xapproachesinfinity):

i mean extrema no critical points in general

OpenStudy (studygurl14):

I thought a criticall point was where g'(x) = 0

OpenStudy (xapproachesinfinity):

no g' is never zero, and yes critical points are found with g'=0 or g' does not exist

OpenStudy (xapproachesinfinity):

here g' is defined for all x and g' does not equal zero hence no critical points

OpenStudy (xapproachesinfinity):

oh one second i didn't see -1<=x<=1

OpenStudy (xapproachesinfinity):

there is max and min in this case

OpenStudy (xapproachesinfinity):

g(-1) and g(1) are max and min respectively

OpenStudy (xapproachesinfinity):

but still we say critical point don't exist

OpenStudy (studygurl14):

Okay, so what would I say to answer the second part of the question?

OpenStudy (xapproachesinfinity):

if we are just talking about extrema absolute max and min exist

OpenStudy (xapproachesinfinity):

the question asked you for extrema first critical points don't exist for second part

OpenStudy (xapproachesinfinity):

stationary point are critical points where g'=0 i just learned that know lol :)

OpenStudy (xapproachesinfinity):

i mean i never heard stationary before

OpenStudy (studygurl14):

Ok, thank you

OpenStudy (xapproachesinfinity):

welcome :)

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